What this comes down to
- Whatever an exterior door is made of, the flashed sill beneath it decides how long the door lasts.
- A foam-core steel or fiberglass door insulates at better than five times the value of solid wood, per the State of Illinois.
- Wood rots at the bottom rail, steel rusts where paint breaks, and fiberglass skins do neither.
- The U-factor on the NFRC label is the number to compare, and on a door lower is better.
- A storm door costing about $200 or less pays off on an old door and adds little to a new foam-core one.
- Perfect Work lists exterior door replacement from $695 installed and front entry doors from $1,295.
Wood, steel and fiberglass all make a good exterior door, and each one fails in its own way. Wood swells and rots, steel dents and rusts, and fiberglass can crack under a hard knock. The right choice depends on the entry.
This guide compares the three on insulation, weather, upkeep and cost. It draws on the State of Illinois, ENERGY STAR and the National Fenestration Rating Council. A national laboratory supplies the sill advice. Storm doors are covered too.
Which exterior door material is best?
For most DuPage County homes, a foam-core fiberglass or steel door is the best value. Both insulate far better than solid wood and need less upkeep. Wood earns its place where looks matter more than maintenance.
The state guidance on doors calls an insulated metal or fiberglass door a better buy than wood. It names them as more durable and lower in upkeep. That is a point in their favor.
No material survives a bad installation. A door hung on a soft sill, or on a sill with no flashing, fails early whatever it is made of. The sill section below explains why.
How much do the three materials differ on insulation?
Foam-core steel and fiberglass doors insulate far better than solid wood. The State of Illinois measures a 1-1/2 inch door without a window. It rates that door at better than five times the insulating value of solid wood.
Most steel and fiberglass entry doors rate about R-5 to R-6, not counting any window. A common build is a steel skin over a polyurethane foam core. Installed right and not bent, the state says it needs no further weatherstripping.
Glass changes the math. The state says glass and patio doors lose heat much faster. Extra panes and low-e coatings improve them two to three times. They still trail a foam-core door.
A rating is easier to compare than a material name. ENERGY STAR says its doors go through independent testing and certification. The test procedures come from the National Fenestration Rating Council. Its label shows a U-factor.
The NFRC explains that its door scale runs from 0.00 to 2.00, and that a lower number is better. That door U-factor scale applies to wood, steel and fiberglass alike.
Which material holds up best in Illinois weather?
None of them wins outright. Wood rots when the bottom rail stays wet, so its finish has to be kept sound. Steel dents, and rust follows wherever the paint breaks at the bottom edge. Fiberglass skins neither rot nor rust.
Fiberglass has its own weak point. A hard knock can crack the skin, and a deep crack lets water reach the core. A wood door can be planed, sanded and refinished. The other two allow very little trimming.
Upkeep follows the same split. Illinois guidance lists steel and fiberglass as the lower-maintenance choice. A wood door wants its finish checked every year. The bottom edge matters most, because that is where water sits.
Why does the sill matter more than the material?
Water reaches the sill first, and a failed sill rots whatever door sits on it. The Building America Solution Center calls the sill the location most vulnerable to water intrusion. The Pacific Northwest National Laboratory runs that center.
Its guide to flashing doors says to flash the head and jambs like a window. It says to set the sill on a pan with a back dam at the inside edge. A sloped pan is required where the sill is deeper than 6 inches.
The same guide recommends metal door assemblies where insects are a problem. Steel and fiberglass hold up at the bottom edge, but they cannot make a soft sill sound. The rotted door frame signs show how to check.
Does a storm door change the choice?
For an old door in good condition, yes. For a new foam-core door, rarely. The State of Illinois calls a storm door costing about $200 or less generally a good investment. It says that holds for an old door.
A new or pricier storm door on a modern foam-core door saves very little, the state adds. It also warns against a glass storm door on a door in direct sun for more than a few hours a day.
Wood storm doors need more upkeep than aluminum, steel or fiberglass frames. The guide to threshold replacement covers the other part of an entry that wears out.
How do wood, steel and fiberglass compare?
| Material | Insulation | Weak point | Upkeep |
|---|---|---|---|
| Solid wood | Lowest of the three | Rot at the bottom rail, swelling in humid weather | Refinish and reseal often |
| Steel with foam core | About R-5 to R-6 | Dents, and rust where paint breaks | Touch up scratches |
| Fiberglass with foam core | About R-5 to R-6 | Cracks under a hard knock | Refinish when the finish fades |
| Any material on a bad sill | Unchanged | Soft sill and no flashing | Repair the sill first |
What does each choice cost?
Perfect Work Remodeling & Repairs lists exterior door replacement from $695 installed. Front entry doors start at $1,295. The door itself moves those numbers most. These are starting prices, not quotes.
| The work | Starting price | What moves it |
|---|---|---|
| Exterior door replacement, installed | From $695 | Material, size and whether the frame is reused |
| Front entry door replacement | From $1,295 | Glass, sidelights and hardware |
| Storm door replacement, installed | From $295 | Opening size and closer type |
| Rotted door frame repair, localized | From $249 | How far the rot runs into the sill and jamb |
| Handyman hourly rate | $65 per hour | Hours on site and materials |
| Minimum service call | $99 minimum | One visit and travel |
Rot found at the sill adds to the door price. The door replacement cost guide itemizes the range. The guide to repairing or replacing a door shows where the line falls.
What cannot be determined from the surface?
What sits inside a door. A skin hides the core. A dented steel door can have a sound core, and a cracked fiberglass skin can have a wet one. Only a closer look settles it.
The condition of the sill is the other unknown. It stays hidden under the threshold until the threshold is lifted. No door material changes that, and a sill that fails inspection changes the job.
Exterior door material questions
Is a steel door or a fiberglass door better?
Neither wins on insulation, since both are about R-5 to R-6 with a foam core. Steel dents and can rust at the bottom edge. Fiberglass resists dents and rust but can crack under a hard impact. Pick on how the entry gets used.
How does Perfect Work choose a door material?
Perfect Work Remodeling & Repairs checks the sill and frame before the door is chosen. A sound frame lets any material work. A soft sill gets repaired first. Entry exposure, sun and glass then decide between wood, steel and fiberglass.
Are wood doors bad for insulation?
A solid wood door insulates far less than a foam-core door. The State of Illinois rates a foam-core door at better than five times solid wood of the same size. A wood door still suits an entry kept sheltered and well finished.
What does a door replacement from Perfect Work include?
Perfect Work Remodeling & Repairs prices the door, the hanging, the seal and the trim. Exterior door replacement starts at $695 installed. Rot found in the sill or jamb is added once it is seen, not before, and the price says so.
Does the material change the U-factor?
Not by name alone. The NFRC label rates each finished door, and lower is better on a scale of 0.00 to 2.00. A foam-core steel or fiberglass door usually rates well. Glass in a door raises the number, which is worse.
Do I need a storm door on a new door?
Usually not. The State of Illinois says a new or pricier storm door on a modern foam-core door saves very little. On an old door in good condition, a storm door costing about $200 or less is generally worth it.
Choose the sill first, then the door
A door material only performs as well as the opening it sits in. Checking the sill and frame first keeps money out of a door the opening cannot support. It also keeps the repair bill small.
A visit from Perfect Work Remodeling & Repairs starts at the sill and the frame. The door repair services page lists the work that can follow once the opening is sound.
Call Perfect Work at 630-297-7888 · Book a door check